Transdominant genetics using expression libraries may identify sequences that modulate plant traits in commercially important ways such as increased resistance to stress, herbicides, pathogens, or predators. To test this genetic strategy, Arabidopsis thaliana will be used as a model system and peptide expression libraries will be introduced by conventional gene transfer procedures. Prior to screening for mutant phenotypes, a variety of technical issues will be examined including generation of large numbers of independent transformants and construction of suitable expression libraries. These experiments are a prelude to studies aimed at discovery of novel genetic agents that can be delivered by genetic engineering into commercially important plant genomes. PROPOSED COMMERCIAL APPLICATIONS: The proposed research may provide a route to identify novel genetic agents that modulate commercially important plant traits such as stress tolerance, pathogen resistance, and herbicide resistance. Ultimately, the work may impact food production and cost.